近30 a江苏夏季降水日变化的气候学特征

基于1980—2013年江苏省61站小时降水资料,分析了江苏省夏季降水日变化的特点及小时极端降水、不同级别雨日的日变化特征。结果表明,江苏省夏季降水日变化具有显著的双峰分布特征,然而江苏省北部和南部降水的主峰时段并不一致。从降水频次、累积降水量来看,江苏省北部降水以清晨至早上时段为主峰、午后至傍晚时段为次峰,南部降水与之相反。长持续性降水占夏季降水的2/3左右,且江苏北部占比多于南部,均为清晨至早上的单峰分布;短持续性降水占夏季降水的1/3,在江苏北部呈现出以午后至傍晚为主峰,清晨至早上为次峰的双峰分布,而在江苏南部呈现出以午后至傍晚的单峰分布特点。小时极端降水,阈值分布南低北高,虽然频次较少,但占夏季降水的40%左右。小时极端降水日变化的双峰分布和夏季总体降水分布类似,但主峰大都出现在午后至傍晚。不同级别雨日的日变化分布各有不同,但全省各区无显著差异。累积降水量贡献主要来自于暴雨和大雨。暴雨无论是从降水频次、累积降水量还是降水强度都呈现清晨至早上的单峰分布。

Climatic features of diurnal variation of rainfall in Jiangsu province during summer for recent 30 years

Using hourly rainfall record of 61 meteorological stations in Jiangsu province, the characteristics of diurnal variation of rainfall is analyzed, including the characteristics of diurnal variation of the hourly extreme precipitation and levels of daily precipitation. The results are as follow. There are two peaks of diurnal variation of precipitation over Jiangsu province during summer. However, the diurnal phase of major peak exhibits regional differences. In the field of accumulated precipitation amount (hereafter as APA) and precipitation frequency, the peak between early morning and morning is much more remarkable over northern Jiangsu province than over the southern part. The APA of long-duration precipitation event amounts to about two-thirds of total precipitation. Also the proportion over the northern Jiangsu is larger than that over the southern part, and peaks always appear during early morning and morning. The short-duration events over northern part have two peaks:the major one is during afternoon and evening, and the minor one is during early moring and moring. However, the short-duration events over southern part provides only one peak during afternoon and evening. The thresholds of hourly extreme precipitation are larger (smaller) over northern (southern) part of Jiangsu, and the peaks always happen in the morning (afternoon and evening) in the northern (southern) part. Although the frequency of hourly extreme precipitation is negligible, but the APA is about 40% of total precipitaion. Major peaks of hourly precipitation occur in the afternoon to evening, and its two peaks of diurnal variation is just like the total precipiation. Besides, diurnal variations for each level of daily precipitation are different, but the distribution in Jiangsu is similar. The APA mainly comes from heavy rain and torrential rain. The frequency and APA of the torrential rain both have peaks in the morning.